Field
The present disclosure relates to the removal and storage of a chimney of a reactor pressure vessel (RPV) during a boiling water reactor (BWR) outage.
Description of Related Art
FIG. 1 is cutaway view of a conventional reactor pressure vessel. Referring to FIG. 1, the reactor pressure vessel 100 includes a core plate 118 within the core shroud 114. The core plate 118 is a circular plate with round openings and supports, inter alia, control rods and fuel assemblies including a plurality of fuel rods 116. The core plate 118 supports the core shroud 114 and may also be bolted to a support ledge in the core shroud 114. The core plate 118 also forms a partition within the core shroud 114, which causes the recirculation flow to pass into the fuel supports and through the fuel assemblies. The core shroud 114 is a cylindrical structure that separates the upward flow of coolant through the core from the downcomer annulus flow. A top guide 112 is bolted to the top of the core shroud 114. The top guide 112 is a grid structure that provides lateral support to the top of the fuel assemblies. Each opening in the grid structure of the top guide 112 can provide lateral support and guidance for four fuel assemblies (or in the case of peripheral openings, two or three fuel assemblies). A chimney 108 is a relatively long cylindrical structure that supports the steam separators 104 and is bolted to the top guide 112. Chimney partitions 110 are located inside the chimney 108 and are in the form of a single structure. The chimney partitions 110 act to channel the mixed steam and water flow exiting the core to limit the cross flow and minimize the potential for recirculating eddies. The steam separators 104 are on the chimney 108 and cover the plenum region 106. The steam separators 104 include a flat base (or a small dome) with an array of standpipes thereon and a separator structure at the top of each standpipe. The steam separators 104 separate the liquid water from the steam-water mixture rising therethrough. Steam from the steam separators 104 flows upward to the steam dryers 102 where additional moisture is removed and directed into a downcomer annulus between the outer wall of the chimney 108 and the inner wall of the reactor pressure vessel 100.
During a reactor outage such as a refueling outage, internal structures of the reactor pressure vessel 100 such as the chimney 108 and chimney partitions 110 need to be removed to access the fuel rods 116. However, the relatively large size of the chimney 108 and chimney partitions 110 therein may present issues with removal and storage during the reactor outage.